EVALUATION OF FIQUE FIBERS ELASTICITY MODULUS WITH DIFFERENT DIAMETERS BY WEIBULL ANALYSIS

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1 EVALUATION OF FIQUE FIBERS ELASTICITY MODULUS WITH DIFFERENT DIAMETERS BY WEIBULL ANALYSIS M. C. A. Telles 1, P. A. Netto 1, G. R. Altoé 1, F. M. Margem 1, S. N. Monteiro 2, A. L. Puglia 3 giulioaltoe@gmail.com 1 - State University of the Northern Rio de Janeiro, UENF. 2 - Military Institute of Engineering, IME, 3 Censa Graduating Institute of Education, ISECENSA. ABSTRACT Since environmental issues are becoming more and more important worldwide, Nowadays Natural fibers are been used to substitute the synthetic ones. Although fique fiber is an important natural fiber and its mechanical properties surpass in various aspects some other lignocelluloses fibers, such few studies have been conducted with the fiber obtained from leaf of fique plant. In order to better evaluate the mechanical properties and possible applications, this paper aims to improve the elastic modulus of the fique fiber by Weibull statistics, by evaluating their mechanicals properties and possible applications. The fibers were divided in diameter intervals and the tensile strength and elastic modulus were measured in each range. The fractured surface was examined using scanning electron microscopy. The results, interpreted by the Weibull statistical method, showed a correlation between the fiber elastic modulus and its diameter. Keywords: fique fiber; tensile test; Analysis of Weibull modulus of elasticity 3697

2 INTRODUCTION The composites are currently constitute the class of materials which develops more in view of the wide combination of properties "engineered", or programmed in advance by design, cannot be obtained in conventional monolithic ceramic based materials, polymers and alloys. In particular, the composites reinforced with synthetic fibers, can achieve superior mechanical properties to other materials. Glass fibers are the most used in cheaper composites for numerous products. The production and processing of synthetic fibers require substantial amount of related with great energy CO2 emissions, the main gas responsible for the greenhouse effect and causing global warming and climate change (1). In addition, composites of glass fibers, specifically, they are difficult to be recycled or incinerated to recover energy (2). Remember also, that the fiberglass can cause health problems such as respiratory diseases. According to Kalia, Kaith e Kaurs (3) cellulose-based fibers are being used due to its "green" image. Instead of glass fibers, widely used in modern technology, the lignocellulosic fibers are renewable and can be incinerated at the end of material useful life without the addition of air pollution, since the amount of CO 2 liberated during the incineration is negligible compared to the amount absorbed by the plant throughout its life. The Fique fibers is an Colombian fiber, extracted from leaf of fique plant (Furcraea Andina), this last one is very used to protect the soil and the fibers for making ropes, sacks and crafts. As other natural fibers, that are currently used in production of composite reinforcement for automobile parts as well as building construction panels and furniture (4-9), the fique one can also be a potential composite reinforcement. However little is known about Fique fiber properties, by this reason this work aims to evaluate the medium and characteristic density of the Fique fiber, analyzing the elasticity modulus and the influence of the diameter on this property. EXPERIMENTAL PROCEDURE The basic material used in this work was the fiber extracted from the leaf of Fique plant (Furcraea Andina), Fig. 1(a), supplied by a producer in Colombia. The fique fibers, Fig. 1(b) are extracted manually from randomly selected 100 fibers, the 3698

09 to 0.30mm. For each interval of equivalent diameter in Fig.

3 equivalent diameter corresponding to the average between the larger and smaller (90º rotation) cross section dimensions at five locations for each fiber, was measured in a profile projector Nikon 6C. (a) Figure 1. Fique plant(a) and its fibers(b). (b) The histogram in Fig. 2 shows the frequency of diameter distribution of fique fibers used in the present work. The fiber diameter varies from 0.09 to 0.30mm. For each interval of equivalent diameter in Fig. 2, 20 fibers were selected and all fibers were individually tensile tested at a temperature of 25 2 o C in a model 5582 universal Instron machine. Especial tensile grips were used to avoid both slippage and damage of the fiber. The values obtained for the elastic modulus were interpreted by means of the Weibull statistics using the computer program Weibull Analysis. Figure 2. Distribution frequency of fique fibers equivalent diameter. 3699

4 ln[ln(1/reliability)] 21º CBECIMAT - Congresso Brasileiro de Engenharia e Ciência dos Materiais RESULTS AND DISCUSSION Based on the maximum load, the tensile strength (σ m ) was determined for each fiber. With this last one and the deformation values, E m was determined then statistically analyzed by means of the Weibull method for the 20 fibers associated with each of the seven diameter intervals shown in the histogram of Fig. 2. The Weibull Analysis program provided the probability plots of reliability vs. location parameter shown in Fig. 3 for all diameter intervals. Here it should be noted that all plots in Fig. 3 are unimodal, i.e. with just one single straight line fitting the points at each interval. This indicates similar mechanical behavior of fibers within the same diameter interval. 0.09<d< <d< <d< <d< <d< <d<0.27 ln(x Location Parameter) 0.27<d<0.30 Figure 3. Weibull graphs for the different intervals in the histogram of Fig

5 In addition, the program also provided the corresponding characteristic elasticity modulus (θ), the Weibull modulus (β) and the precision adjustment (R 2 ) parameters. The values of these parameters as well as the average elasticity modulus (E m ) and associated statistical deviations, based on the Weibull distribution, are presented in Tab.1. Table 1. Weibull parameters for the elasticity modulus fique fibers associated with different diameters. Characteristic Weibull Diameter interval Elasticity Modulus, (mm) Modulus, β θ (GPa) Precision Adjustment R 2 Average Statistical Elasticity Deviation Modulus (GPa) 0,09 0,12 2,372 3,836 0,9304 3,400 1,525 0,12 0,15 3,859 2,251 0,9664 2,036 0,590 0,15 0,18 2,572 2,077 0,9497 1,844 0,769 0,18 0,21 2,332 1,876 0,9801 1,662 0,757 0,21 0,24 3,533 1,758 0,9570 1,583 0,496 0,24 0,27 4,549 1,819 0,9755 1,661 0,415 0,27 0,30 4,467 1,407 0,9222 1,283 0,325 The variation of the characteristic elasticity modulus with the average fiber diameter for each one of its intervals is presented in Fig. 5. In this figure there is a tendency for the θ parameter to vary inversely with the average fique fiber diameter. This means that the thinner the fiber the higher tends to be the characteristic elasticity modulus. Furthermore, the corresponding values of β and R 2, shown in Tab.1, statistically support the inverse correlation between θ and the average diameter d (mm). By means of a mathematic correlation, a hyperbolic type of equation was proposed to fit the data in Fig. 4. Ɵ (Gpa)= (0,34 d) + 0,18 (A) 3701

6 Figure 4. Variation of the characteristic elasticity modulus with the mean diameter for each interval in Fig.2. In order to analyze the physical meaning of Eq. (A), the average elasticity modulus, E m, evaluated in this work for the fique fibers was plotted as a function of the diameter in Fig. 5. In this figure an apparent hyperbolic inverse correlation also exists between E m and d within the error bars (statistical deviations) and investigated limits. an unequivocal hyperbolic inverse correlation also exists between E m and d. E m (Gpa) = 0,30 d +0,21 (B) Figure 5. Variation of the mean elasticity modulus with the diameter for each interval in Fig

7 Based on Eq. (A) and (B) it is suggested that, as in others lignocellulosic fibers (10, 11), a hyperbolic type of mathematical equation is the best statistical correlation between the elasticity modulus and the diameter of leaf fique fibers. CONCLUSIONS A Weibull statistical application to analysis of elasticity modulus revealed an inverse hyperbolic correlation with the equivalent diameter of fique fibers The experimental results obtained for both the elastic modulus characteristic as for the average maximum modulus, showed a hyperbolic equation with similar coefficients. Statistically, the larger distribution of fibrils mechanical resistances of the thicker fiber allows a weaker fibril to rupture shortly than any of the fewer fibrils of the thinner fiber. REFERENCES 1. A. Gore, An Inconvenient Truth. The Planetary Emergency of Global Warming and What We Can do About It (Emmaus, Pennsylvania, USA: Rodale Press, 2006). 2. MONTEIRO S.N.; LOPES, F.P.D.; FERREIRA, A.S.; NASCIMENTO, D.C.O. Natural fiber polymer matrix composites: cheaper, tougher and environmentally friendly. JOM, v. 61, n. 1, p , S. Kalia, B. S. Kaith, I. Kaurs, Cellulose Fibers: Bio and Nano Polymer Composites ( New York: Springer, 2011). 4. S.N. Monteiro, F.P.D. Lopes, A.S. Ferreira, D.C.O. Nascimento, Natural fiber polymer matrix composites: cheaper, tougher and environmentally friendly, JOM, 61 (2009) A.K. Bledzki, and J. Gassan, Composites Reinforced With Cellulose-Based Fibers. Prog. Polym. Sci, 4 (1999) D. Nabi Sahed and J.P. Jog, Natural fiber polymer composites: a review, Advances in Polymer Technol., 18 (1999),

8 7. A.K. Mohanty, M. Misra and G. Hinrichsen, Biofibers, biodegradable polymers and biocomposites: an overview, Macromolecular Mat. And Engineering, 276/277 (2000), S.J. Eichhorn, C.A. Baillie, N. Zafeiropoulos, L.Y. Mwakambo, M.P. Ansell, A. Dufresne, Review of current international research into cellulosic fibres and composites, J. Mater. Science, 36 (2001) A.K. Mohanty, M. Misra and L.T. Drzal, Sustainable biocomposites from renewable resources: opportunities and challenges in the green material world, J. Polym. Environ., 10 (2002), S. N. Monteiro, K. G. Satyanarayana, F. P. D. Lopes High strength natural fibers for improred polymer matrix composites Mat. Sei. Forum (2010) D.C.O. Nascimento, L.C. Motta, S.N. Monteiro, Weibull analysis of tensile tested piassava fibers with different diameters, Proceedings of the Characterization of Minerals, Metals & Materials TMS Conference 2010 (Seattle, WA, USA, February 2010)

Diameter dependence of tensile strength by Weibull analysis: Part II jute fiber

ISSN 1517-7076 Revista Matéria, v. 15, n. 2, pp. 125-131, 2010 http://www.materia.coppe.ufrj.br/sarra/artigos/artigo11205 Diameter dependence of tensile strength by Weibull analysis: Part II jute fiber